|I have had creeping phlox planted for 6-7 years and for the last couple years there has been so much dead stuff in it that I am tempted to dig it all up. I have heard that creeping phlox has a certain life span and, if so, is it time to dig mine?
It's more likely that the soil has been depleted after many years of having the same plant pulling the same nutrients. If your plot of Phlox looks really bad, though, it's best to start from scratch, or save some of the good looking plants to reestablish the bed. Phlox are heavy feeders in general; the creeping varieties are no exception, though they're often planted in the poor soils preferred by other rock garden plants. Their roots are shallow, so if the top few inches of soil isn't rich, they'll start to flag. Enrich the bed with compost/aged manure and a slow-release, balanced organic fertilizer. Keep the new planting well watered this season, and next year, after it's rush of spring bloom, trim the plants with garden shears by about a half. This will encourage more root growth, and keep the plants neat and healthy. Each season, add more compost to the bed and water during dry spells, and the next round should last you a long while. Enjoy!